Trying to squeeze in some more features

src/graphics_engine.v

@@ -10,21 +10,40 @@ module graphics_engine(
     input wire [6:0] video_modes
     );
 
+    localparam [17:0] cyclic_rgb_channel = 18'b01_10_11_11_11_11_11_11_10;
+
     wire mode_toggle_animation = video_modes[6];
-    wire mode_toggle_daynight = video_modes[5];
+    wire mode_toggle_bg_style = video_modes[5];
     wire mode_toggle_text_style = video_modes[4];
     wire mode_toggle_overlay = video_modes[3];
     wire mode_toggle_big_sine = video_modes[2];
     wire mode_toggle_little_sine = video_modes[1];
     wire mode_negative = video_modes[0];
 
     wire [5:0] sine_off_y, sine_bg_off_y;
+
+    wire [7:0] xy_avg;
+    wire [3:0] cycle_red_colour, cycle_green_colour, cycle_blue_colour;
 
-    wire [5:0] overlay_rgb, sine_rgb, sine_bg_rgb, sine_rgb_dither, sine_bg_rgb_dither;
+    wire [5:0] overlay_rgb, sine_rgb, sine_bg_rgb, sine_rgb_dither, sine_bg_rgb_dither, bg_rgb;
     wire overlay_active, overlay_text_active, sine_active, sine_bg_active;
 
     reg [9:0] ctr;
     wire [9:0] anim_x, anim_2x;
+
+    assign xy_avg = anim_x[8:2] + y[8:1];
+    assign cycle_green_colour = xy_avg[3:0];
+    assign cycle_red_colour = cycle_green_colour - 4'd6;
+    assign cycle_blue_colour = cycle_green_colour + 4'd6;
+
+    reg [5:0] cycle_rgb;
+    always @(*) begin
+        cycle_rgb[5:4] = (cycle_red_colour < 4'd9) ? cyclic_rgb_channel[{cycle_red_colour, 1'b0}+:2] : 2'b00;
+        cycle_rgb[3:2] = (cycle_green_colour < 4'd9) ? cyclic_rgb_channel[{cycle_green_colour, 1'b0}+:2] : 2'b00;
+        cycle_rgb[1:0] = (cycle_blue_colour < 4'd9) ? cyclic_rgb_channel[{cycle_blue_colour, 1'b0}+:2] : 2'b00;
+    end
+
+    assign bg_rgb = cycle_rgb & {6{(x[0] & y[0])}};
 
     reg en_v_sync;
     always @(posedge clk, negedge rst_n) begin
@@ -69,9 +88,10 @@ module graphics_engine(
         .y(sine_bg_off_y[4:0])
     );
 
-    assign overlay_rgb = overlay_active ? {
-      {overlay_text_active, ctr[7], overlay_text_active, ctr[6], overlay_text_active, ctr[5]}
-    } : 6'b00_00_00;
+    assign overlay_rgb = overlay_active ? (
+        mode_toggle_text_style ? cycle_rgb & {3{overlay_text_active, 1'b1}} : 
+            {overlay_text_active, ctr[7], overlay_text_active, ctr[6], overlay_text_active, ctr[5]}
+    ) : 6'b00_00_00;
 
     assign sine_rgb_dither = sine_rgb & {6{(x[0] | y[0])}};
     assign sine_bg_rgb_dither = sine_bg_rgb & {6{(x[0] & y[0])}};
@@ -82,10 +102,11 @@ module graphics_engine(
     assign {r, g, b} = frame_active ? (
         (overlay_active & ~mode_toggle_overlay) ? overlay_rgb : (
             sine_active ? sine_rgb_dither : (
-                sine_bg_active ? sine_bg_rgb_dither : 6'b00_00_00
+                sine_bg_active ? sine_bg_rgb_dither : 
+                    mode_toggle_bg_style ? bg_rgb : 6'b00_00_00
             )
         )
     ) ^ {6{mode_negative}} : 6'b00_00_00;
 
-    wire _unused = &{sine_off_y[5], sine_bg_off_y[5], anim_x[9], anim_x[2:0], anim_2x[9:8], anim_2x[1:0], mode_toggle_text_style, mode_toggle_daynight};
+    wire _unused = &{sine_off_y[5], sine_bg_off_y[5], anim_x[9], anim_x[2:0], anim_2x[9:8], anim_2x[1:0], xy_avg[7:4]};
 endmodule